Data synchronisation adds complexity to offline applications, which is why you need to decide whether synchronisation is a requirement or whether the application data can stand alone.
Self-contained applications will store the data on the device, and do not need to synchronise the data.
You also need to consider how data synchronisation will operate, and when the application will synchronise the data.
Other issues you need to consider are:
o Will users synchronise to their own database?
o How do you ensure offline transactions synchronise in the correct sequence?
o How do you resolve synchronisation conflicts?